Fabric Startup Crash: WindowsException (AccessDeniedException or NoSuchFileException)

What the log looks like

sun\.nio\.fs\.WindowsException\.translateToIOException[\s\S]{1,1500}at net\.fabricmc\.loader\.impl\.
java\.nio\.file\.(?:AccessDeniedException|NoSuchFileException):[^\r\n]+[\s\S]{1,300}sun\.nio\.fs\.WindowsException\.translateToIOException[\s\S]{1,1500}net\.fabricmc\.loader\.impl\.

How to fix it

1. Find the `Caused by: java.nio.file.NoSuchFileException:` or `AccessDeniedException:` line in your crash log and inspect the exact folder path shown after it.
2. If your launcher profile or folder name contains an exclamation mark (`!`)—for example `profiles\Shaders!`—duplicate or recreate the profile using only plain letters and numbers, as `!` breaks Java and Fabric jar remapping.
3. If the path points to `.fabric\remappedJars` or `client-intermediary.jar.tmp`, close your launcher completely, open your instance folder, and delete the `.fabric` folder so Fabric rebuilds its cache cleanly on the next launch.
4. If the error says `Could not create directory` (such as `...\iris-reserved\1.19.4`), open that Minecraft instance folder in File Explorer and manually create the missing parent folder (e.g., `iris-reserved`), or verify your launcher's Game Directory setting points to an existing folder.
5. If you get `AccessDeniedException` on `.minecraft\libraries` or `.tmp` files, end any stuck `javaw.exe` processes in Task Manager, ensure your Minecraft data is not inside a OneDrive-synced folder, and add your launcher data directory to your antivirus exclusions.

Check your own log